The present invention relates to bumper reinforcement beams used in vehicle bumper systems, where the beam is tubular and has a single (mono) center leg. The present invention also relates to roll forming apparatus and methods of forming said beams. However, the present invention is not believed to be limited to only bumper reinforcement beams for vehicles.
Modern vehicle bumper systems typically include a reinforcement beam designed for strength and impact characteristics in order to meet government and insurance industry standards for particular vehicles, but also designed to minimize overall vehicle weight, to maximize strength-to-weight ratios, to fit within confined vehicle package spaces, and to satisfy vehicle aesthetic and functional requirements at front and rear ends of vehicles. Concurrently, the processes and methods of manufacturing the beams preferably minimize undesired product dimensional and quality variations, while also minimizing manufacturing cost, optimizing manufacturability and minimizing scrap. Roll forming processes and methods have proved to be particularly effective at producing high volume runs of bumper reinforcement beams with competitive cost and high dimensional consistency. However, the industry is very competitive, such that even small improvements can be important.
Further, many of the desired features above are conflicting, such that it is not clear how to improve a particular bumper reinforcement beam, or how to improve the roll forming process for making the beam. For example, a heavier beam may be stronger, but would cause an unacceptable increase in vehicle weight. High strength materials may be preferred, but they are expensive, difficult to form, and cause high wear on tooling. Accurate control over positioning of sheet edges during the roll forming process is desired to facilitate an accurate beam cross-sectional shape, to reduce tolerances along the edges so that excess material along the edges can be reduced in order to minimize beam weight, and to facilitate consistent contact during welding. However, this can require extra roll forming steps and stations as well as additional tooling, hardware and software controls, each of which increase capital investment and make the roll forming process more complex. The above beams include two sheet edges formed against other material of the sheet, with each being welded by a welder to permanently form the tubular shape of the beams. However, welders take up space along the roll form apparatus, especially where the welders are positioned at different stations along a length of a roll form apparatus, thus increasing floor space requirements considerably, as well as capital investment. Nonetheless, it is difficult to weld in two opposing sides of a beam due to flying debris adversely affecting one or both of the welders. Notably, welds must be consistent and reliable in order to provide reliable and consistent impact strength in the bumper reinforcement beams and in the related bumper systems.